Motor starting switch

ABSTRACT

A motor starting switch installable, for example, on a fractional horsepower electric motor and actuable between a run and a start position by means of a centrifugal actuator axially shiftable on the rotor shaft of the motor in response to start up or shut down of the motor. The starting switch includes a rotary actuator member having a cam follower engageable by a conical cam surface on the centrifugal actuator as the latter shifts axially from its run to its start position thereby to effect rotary movement of the actuator member and to effect actuation of the switch from its run to its start position as the centrifugal actuator moves through only a portion of its stroke. The rotary actuator member is further engageable with a cylindrical cam surface of the centrifugal actuator after the switch has been converted to its start position thereby to prevent overstressing of a switch arm within the starting switch upon continued movement of the centrifugal actuator to its start position.

BACKGROUND OF THE INVENTION

This invention relates to a switch for a dynamoelectric machine, andmore particularly to a starting switch for a fractional horsepowerinduction electric motor.

Typically, capacitor start and split phase induction motors have a runwinding and a starting winding placed in winding receiving slotsprovided in the bore of the stator core of the motor. The startingwinding is energized during start up of the motor (or when the speed ofthe motor falls below a specified operating speed) so as to create arotating field in the stator and to apply sufficient torque to the rotorfor starting purposes. However, once the motor has accelerated to adesired operating speed, (e.g., this speed may be about 80 percent ormore of the normal operating speed of the motor), the rotor is able tofollow the alternations of the magnetic field created by the runwindings, and the starting winding no longer is needed. Typically, thestarting winding is not intended for continuous use and may fail if notdeenergized during normal operation of the motor. As is conventional, aswitch, referred to as a motor starting switch, is provided in the motorfor energizing the starting winding only during start up of the motorand for deenergizing the starting winding once the motor has attainedits desired operating speed. These motor starting switches areconventionally actuated by a centrifugal actuator mounted on androtatable with the rotor shaft of the motor, the centrifugal actuatorbeing responsive to the speed of the motor for actuating the startingswitch from its start to its run position in response to the motorattaining a predetermined operating speeed. Centrifugal actuatorstypically include an actuator member movable axially on the rotor shaftfrom an off or stop position when the motor is stopped (or is operatingbelow a specified operating speed) to a run position upon the motoraccelerating to a predetermined operating speed. Typically, an actuatorlinkage operatively interconnects the motor starting switch and theactuator member of the centrifugal actuator. As shown in the co-assignedU.S. Pat. No. 4,034,173, this linkage may include a leverinterconnecting the switch and actuator member, a spring, and means foradjusting the lever with respect to the actuator. In some instances, thelever is pivoted on a portion of the motor itself, for example on theend shield of the motor. These parts must of necessity be installedbefore the motor starting switch has been installed in the motor duringmanufacture thereof.

Because the actuator member of the centrifugal actuator moves only alimited distance between its off and run positions, it has heretoforebeen necessary to accurately adjust the relative positions of the motorstarting switch and the centrifugal actuator so as to ensure that theformer is properly actuated by the centrifugal actuator at a specifiedmotor operating speed. This adjustment of the centrifugal actuator withrespect to the motor starting switch is a time consuming operation andthus results at least in part in higher labor costs in manufacture ofthe motor. Typically, a centrifugal actuator only exerts a relativelylight force on the linkage interconnecting the actuator member and themotor starting switch. With prior linkage arrangements, the forceexerted on the linkage was, in some instances, too low to actuate themotor starting switch so as to energize the starting winding of themotor upon subsequent start up of the motor. This condition is sometimesreferred to as a "stuck" actuator condition and it prevents the motorfrom starting.

During the service life of a motor, end play (i.e., axial movement) ofthe rotor shaft with respect to the end shields (or the frame) of themotor may develop. This end play may be sufficient so as to appreciablychange the relative position of the centrifugal actuator mounted on therotor shaft and the motor starting switch rigidly mounted on the frameor end shield of the motor thus effecting operation of the motorstarting switch. Under certain end play conditions, the centrifugalactuator could fail to deenergize the starting winding upon the motorattaining its desired operating speed thus causing the starting windingto fail. Under other end play conditions, the centrifugal actuator mayfail to reset the motor starting switch to energize the starting windingupon subsequent start up of the motor and thus the motor would fail tostart.

Also, in certain motor applications (e.g., in a clothes dryer) in whichthe motor starting switch is exposed to lint-laden air, the deposit ofthe lint within the switch has heretofor been a problem. Morespecifically, the motor starting switch is typically installed in alocation within the motor proximate the motor bearing lubrication systemand oil vapor is oftentimes deposited on all of the exterior surfaces ofthe switch including the actuating plunger. Typically, the actuatorplunger of prior art motor starting switches was moveable in axialdirection in and out of the starting housing upon actuation of theswitch, and lint on the plunger was carried into the inside of theswitch housing. Also, prior art motor starting switches have oftentimeshad a large gap between the plunger and the housing through which lintcould readily enter the housing. Upon entering the housing, this lintwould collect on various electrical components within the switch, andcould, on occasion, prevent good contact between the electrical contactswithin the switch thus causing intermittent or improper operation of theswitch, and could, in certain instances, result in failure of the motorto start.

Also, many prior art motor starting switches had a problem ofoverstressing (and thus permanently deforming) one or more of the switcharms within the starting switch upon the moveable switch arm engaging afixed contact prior to completion of the stroke of the centrifugalactuator. Typically, the force of the centrifugal actuator was such,that once the switch arm became stoppd against a fixed electricalcontact, then the centrifugal actuator could continue to apply increasedforce to the switch arm which could drastically increase the bendingmoment on the switch arm. In certain applications it has been found thatthis overstressing was sufficient to cause permanent deformation of theswitch arm and thus the switch arm lost its resilient characteristicswhich biased it toward contact with an opposed fixed contact when themotor was running.

Among the several objects and features of the present invention may benoted the provision of a motor starting switch operable by a centrifugalactuator which requires a relatively low force to actuate it;

The provision of such a motor starting switch which is relativelyinsensitive to end play of the rotor shaft and which need not beaccurately positioned with respect to the centrifugal actuator duringmanufacture of the motor;

The provision of such a motor starting switch in which the force appliedto the contacts of the starting switch by the centrifugal actuator islimited so as to prevent damage to the flexible switch arms carrying themoveable contacts;

The provision of such a starting switch which substantially reduces theentrance of lint and other airborne particles into the interior of theswitch; and

The provision of such a starting switch which is of compact size andrugged construction, which is reliable in operation, which is easy toinstall in the motor, and which has a relatively long service life.

Other objects and features of the invention will be in part apparent andin part pointed out hereinafter.

SUMMARY OF THE INVENTION

Briefly stated, this invention is intended for use with a dynamoelectricmachine, and more particularly with an electric motor such as afractional horsepower induction motor comprising a stator, a rotor, andshaft journal with respect to the stator and supporting the rotor. Thestator assembly includes a main winding and an auxiliary winding, and asis typical, the motor further includes a starting switch operable todeenergize the auxiliary winding upon the motor obtaining apredetermined speed during start up. A centrifugal actuator is mountedon the rotor shaft and is operably connected to the starting switch foractuating the latter in response to the motor attaining itspredetermined speed during start up. The centrifugal actuator has aportion thereof shiftable axially on the shaft of the motor between astarting position and a run position upon start up of the motor and uponthe motor obtaining its predetermined speed, the actuator being furthershiftable in opposite axial direction from its run to its startingposition upon slowing down or stopping of the motor thereby to reset thestarting switch in its starting position. The starting switch has ahousing adapted to be secured in fixed position with respect to thecentrifugal actuator and has at least one switch contact movabletherewithin in response to the movement of the centrifugal actuatorbetween its start position in which the auxiliary winding of the motoris energized and a running position in which the auxiliary winding isdeenergized. Specifically, the improvement of this invention relates toan actuator lever rotatably mounted on the housing which is cooperablewith the movable switch contact and with the axially shiftable portionof the centrifugal actuator for effecting movement of the switch contactbetween its starting and run positions in response to movement of thecentrifugal actuator portion between its staring and run positions. Thecentrifugal actuator shiftable portion has an inclined cam surface whichis engageable with the actuator lever as the centrifugal actuatorportion moves from its run to its starting position for effectingmovement of the movable contact from its run to its starting positionduring only a portion of the stroke of the centrifugal actuator memberas the latter moves from its run to its start position. The centrifugalactuator portion has another surface contiguous to the inclined camsurface with this other surface being generally parallel to thelongitudinal axis of the shaft and being engageable with the rotaryactuator lever after the latter has effected movement of the movableswitch contact to its starting position thereby to hold the movableswitch contact in its starting position substantially without theapplication of additional force to the movable contact as thecentrifugal actuator completes its stroke to its full start position.With the switch housing mounted in fixed position relative to thecentrifugal actuator, the rotary actuating lever is pivoted to thehousing so that the portion of the actuating lever engageable with theinclined and cylindrical cam surface of the centrifugal actuator movesgenerally radially with respect to the longitudinal axis.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view of a motor starting switch of thepresent invention as it is rigidly mounted on the endshields of a motoror other dynamoelectric machine and further illustrating a portion ofthe rotor shaft of the dynamoelectric machine on which is mounted acentrifugal actuator operable to effect actuation of the starting switchbetween its starting and run positions;

FIG. 2 is a vertical longitudinal cross-sectional view of the motorstarting switch and a portion of the centrifugal actuator movablebetween a starting position (as shown in solid lines) and a run position(as shown in dotted lines);

FIG. 3 is a somewhat enlarged front elevational view of the motorstarting switch of the first embodiment with its cover removed in itsstarting position;

FIG. 4 is a view similar to FIG. 3 illustrating a second embodiment ofthe starting switch of the present invention;

FIG. 5 is an enlarged cross-sectional view taken along line 5--5 of FIG.3 illustrating a labryinth seal arrangement for inhibiting the entranceof airborne lint or dust particles into the interior of the startingswitch;

FIG. 6 is a semi-diagrammatic view of a typical dynamoelectric machine(e.g., a split phase induction motor) illustrating the arrangement ofthe main winding and auxiliary windings of the stator assembly of themotor and the connection of the motor starting switch of the presentinvention to the auxiliary windings of the motor; and

FIG. 7 is a front elevational view of another embodiment of the switchof this invention.

Corresponding reference characters indicate corresponding partsthroughout the several views of the drawings.

DESCRIPTION OF PREFERRED EMBODIMENTS

Referring now to the drawings, a first embodiment of a motor startingswitch of the present invention is indicated in its entirety byreference character 1 in FIGS. 1-3. The motor starting switch is shownto be mounted on an endshield 3 of the stator assembly 4 (see FIG. 6) ofa conventional dynamoelectric machine 5, such as a split phasefractional horsepower induction motor. The motor further includes asquirrel cage rotor 6 mounted for rotation within the motor of thestator assembly. The rotor includes a rotor shaft 7 on which the rotoris mounted. The rotor shaft is journaled for rotation in suitablebearings provide in endshields 3 of the stator assembly. The statorassembly, as is conventional, comprises a main winding M and anauxiliary winding AUX. The general arrangement of stator assembly 4 androtor 6 is generally depicted to FIG. 6 and is, of course, well known tothose skilled in the art. For the sake of brevity, a completedescription of the stator and rotor assemblies have been omitted fromthis disclosure.

As shown in FIG. 1 and is generally indicated at 9, a centrifugalactuator is mounted on rotor shaft 7 for rotation therewith. Forexample, the centrifugal actuator may be similar in construction andoperation to the centrifugal actuator disclosed in the coassigned U.S.Pat. No. 3,609,421 to Eugene F. Hildebrandt, one of the inventors of thepresent invention, except for differences as will be hereinafter pointedout. Generally, centrifugal actuator 9 includes a sleeve 11 received onshaft 7 and an actuator collar 13 slidably movable in a longitudinaldirection on sleeve 11 between a start (or off) position (as shown insolid lines in FIG. 1) and run position (as shown in dotted lines inFIG. 2) in response to pivoting movement of centrifugal levers 15a, 15b.These levers are spring biased toward their off position (as shown insolid lines in FIG. 1) by means of tension springs 17 and the levers aresubjected to centrifugal force upon shaft 7 beginning to rotate. Uponthe shaft (and hence the motor) obtaining a predetermined rotationalspeed upon start up of the motor (for example, about 80% of thesynchronous speed of the motor), the centrifugal force acting on levers15a, 15b is sufficient to overcome the bias of spring 17 and thus thelevers pivot about respective pivot points 18 (see FIG. 1) on thecentrifugal actuator so as to effect axial movement of the actuatorcollar 13 in one direction along the longitudinal axis of shaft 7 (i.e.,as shown in FIG. 1) thereby to effect actuation of switch 1 from itsstart to its run position. It will be understood that with the motorstopped and with the starting switch 1 in its starting position, switchcontacts within the switch 1 (as will be hereinafter described indetail) ar in position for energization of both the main winding M andauxiliary winding AUX. With both the main and auxiliary windingsenergized during start up, the motor will generate sufficient torque forstarting purposes. As the motor accelerates to its synchronous operatingspeed, the field generated by the main windings is sufficient tomaintain operation of the motor and thus the auxiliary windings are nolonger needed. Thus, as switch 1 is switched from its start to its runposition, the auxiliary winding is disconnected from the source of thepower by means of the starting switch. Upon the motor slowing below apredetermined speed or upon stopping, spring 17 shift levers 15a, 15band actuator collar 13 from their respective run positions to their offor starting position and again effect the resetting of switch 1 to itsstarting position.

It will be understood that the disclosure of the above-noted coassignedU.S. Pat. No. 3,609,421, as it applies to centrifugal actuator 9 abovedescribed, is incorporated herein by reference and should be referred tofor a more complete disclosure of the construction and operation ofcentrifugal actuator 9.

Specifically, however, centrifugal actuator 9 differs from thecentrifugal actuator disclosed in the above-noted prior patent in thatactuator collar 13 is herein shown to have a generally conical camsurface 19 facing toward motor starting switch 1 (i.e., facing away fromthe direction of movement of collar 13 as it moves from its starting toits run position), and an outer cylindrical holding surface 20 generallycoaxial with the longitudinal center line of shaft 7 and contiguous withconical cam surface 19. It will be understood that conical cam surface19 and cylindrical holding surface 20 are surfaces of revolution aboutthe longitudinal centerline of shaft 7.

Starting switch 1 is shown to comprise a housing or mounting frame 21molded, for example, of a suitable synthetic electrical insulatingresin. The housing is shown to have side walls 23, a bottom wall 25, aback wall 26 and a top wall 27. A removable front cover 29 (see FIG. 2)covers the interior of the housing and various switch contact parts aswill be hereinafter specified. A plurality of terminals is indicated atT₁ -T₅ is fixedly secure in top wall 7. As is conventional, terminals Tare made of suitable sheet metal, are electrically conductive, and aresubstantially rigid to top wall 27. Certain of the terminals carrystationary or fixed contacts, as indicated at 31, 33, and 35, and othersof the terminals support flexible switch arms 37 and 39. These switcharms respectively carry movable electrical contacts 38 and 40 of theirfree ends which in turn cooperate with respective fixed contacts toconstitute a single pole double throw switch (SPDT) as generallyindicated at S₁, and a single pole single throw (SPST) switch S₂.Flexible switch arms 37 and 39 are preferably made of a resilient,electrically conductive sheet metal alloy, such beryllium copper or thelike, and the switch arms are cantilevered from their respectiveterminals T₄ and T₅. Switch arm 37 is formed so that it is normallyspring biased into engagement with its respective fixed contact 33 andswitch arm 39 is so formed that it is spring biased into engagement withits respective fixed contact 35 when centrifugal actuator 9 and hencethe starting switch is in its run position. Thus, when switch 1 of thepresent invention is in its run position, switch arms 37 and 39 assume aposition opposite from that shown in FIG. 1 so that switch S₁ completesa circuit from terminal T₂ to T₄ and so that switch S₂ completes acircuit between terminals T₁ and T₅.

In accordance with this invention, a rotary actuator member, asgenerally indicated at 41, is pivotally mounted with respect to thehousing 21 and is engageable by actuator collar member 13 as the lattershifted between its run and starting positions for flexing switch arms37 and 39 and for making and breaking switches S1 and S2. Preferably,rotary actuator 41 is rigid, unitary one piece member molded of suitablesynthetic resin electrical insulation material. The rotary actuatormember 41 is shown to have a hub 43 with an opening 45 therethrough. Apost 47 integral with back wall 26 of housing 21 extends outwardly fromthe back wall and is disposed generally in the plane of bottom wall 25.An opening 49 is provided in bottom wall 25 for reception of hub 43 ofthe actuator member and, as is generally indicated at G, a relativelysmall gap (e.g., about 0.01 inches or about 0.25 mm.) is providedbetween the edges of the bottom wall defining opening 49 and the outersurface of hub 43. A retainer 48 (e.g., a snap ring) is installable onthe outer end of the post 47 for securely holding rotary actuator member41 on post 47 and for permitting rotary actuator member to freely rotateor pivot on the post or may be retained by switch cover 29.

A lever 51 extends from the bottom of hub 43 and is disposed outside ofhousing 21. Lever 51 has a cam follower, as generally indicated at 53,and its outer or free end is cammingly engageable with conical camsurface 19 and within cylindrical holding surface 20 on actuator collar13. A switch lever 55 extends from the upper side of hub 43 withinhousing 21 and engages both switch arms 37 and 29 so as to effectmovement of the switch arms from their normal positions as when theswitch is in its run position to their flex positions (as illustrated inFIG. 3) when the centrifugal actuator and the switch are in theirrespective start positions.

Switch lever 55 has a stub 57 which extends outwardly therefrom andslidingly engages the bottom face of switch arm 39 so as to open andclose switch S2. Furthermore, a coil compression spring 59 is interposedbetween switch lever 55 and the bottom face of switch arm 37 so as toflex switch arm 39 from engagement with fixed contact 33 to engagementwith contact 31 upon movement of centrifugal actuator 9 from its run toits start position.

In accordance with this invention, it will be observed in FIG. 3 thatrotary actuator member 41 is pivotally mounted on post 47 at somelateral distance from one side of the longitudinal centerline of shaft 7and that cam follower 53 is on the opposite side of the longitudinalcenterline of shaft 7. Thus, the outer end of cam follower 53 is movedgenerally radially with respect to the longitudinal centerline of shaft7 as actuator member moves axially between its start and run positions.

As shown in FIG. 1, cam follower 53 has an inclined cam face 61 and abottom face 63. With centrifugal actuator 9 in its run position and withthe actuator collar 13 shifted to its position shown in dotted lines inFIG. 2, switch arms 37 and 39 resiliently bias rotary actuator member 41to rotate on post 47 in generally counterclockwise direction (as viewedin FIG. 3) and thus cam follower 52 is positioned at or below the levelof inclined cam face 19 on actuator collar 13. Upon slowing or stoppingof the motor and upon movement of actuator collar 13 from its run to itsstarting position, inclined cam face 61 of cam follower 53 is engaged bythe inclined or conical cam face 19 of actuator collar 13. Continuedmovement of actuator collar 13 toward its start position causes camfollower member 53 to ride up cam surface 19. Upon the bottom of edge ofinclined cam face 61 reaching the transition of actuator collar 13between conical surface 19 and cylindrical holding surface 20, thebottom surface 63 of cam follower 53 engages holding surface 20 therebyholding switches 37 and 39 in their start positions (as shown in FIG. 3)as actuator collar 13 continues its movement toward its start positionwithout causing further movement of rotary actuator member 41. In thismanner, switch arms 37 and 39 are positively and quickly moved fromtheir run positions to their start positions during only a portion ofthe stroke or travel of the actuator collar 13 as the latter moves fromits run to its start position. It will be further noted that, due to theinclination of cam surfaces 19 and 61, only a portion of the stroke ofactuator collar 13 is required to actuate switch 1 from its run to itsstart position as the actuator collar moves from its run to its startposition. Thus, so long as cam follower 53 engages actuator collar 13 atsome point along its stroke with sufficient travel of the actuatorcollar remaining so as to effect movement of rotary actuator member 41,the switch will be actuated from its run to its start position. Thus, inaccordance with this invention, the sensitivity of starting switch 1with respect to its axial relation relative to centrifugal actuator 9 isremarkably reduced over comparable prior art starting switcharrangements. Accordingly, the requirement of having to accurately shimswitch 1 with respect to actuator 9 so as to reduce endplay (or so as toadjust actuation of the switch during movement of the centrifugalactuator) is significantly reduced.

Further in accordance with this invention, switch 1 is not as subject todraw significant amounts of airborne lint or dust into the interior ofswitch housing 21, even when the switch is operated in a high dust orlint environment, such as would be present inside the motor of a clothesdryer or the like. More significantly, terminals T of the switch 1 aresubstantially sealed with respect to housing 21 (i.e., the terminals arein close fitting relation with the housing if not hermetically sealedtherewith) so as to substantially block the entrance of dirt laden airinto the housing via the terminal openings. Further, cover 29 fitstightly on housing 21 so as to enclose the switch contacts therewithin.Heretofor, prior art starting switches oftentimes had an axially movableplunger, and the plunger would move in and out of the housing in apumping motion when repeatedly actuated by the amount of movement of theplunger being generally equal to the amount of movement of the switcharms so that any dust clinging to the plunger would be forced inside thehousing. However, in sharp contrast, the rotary actuator member 41 ofthe starting switch of the present invention moves only slightlyrelative to bottom wall 25 of the housing at the point through which theactuator member passes through the housing. As can be seen in FIG. 3,rotary actuator 41 moves through only a slight degree of rotary movement(e.g., about 5 degrees) to effect movement of the switch contacts fromtheir run to their starting positions. Thus, the relative movement ofhub 43 of rotary actuator member 41 with respect to the edges of bottomwall 25 defining opening 49 therein is only a few thousandths of an inchand thus the tendency of "pumping" of lint or dust clinging to rotaryactuator member 41 into the interior of the switch is markedly reduced.Further, a relatively close gap G (e.g., about 0.010 inches or 0.25 mm)is maintained between the edges of bottom wall 25 defining opening 49 inbottom wall 25 so as to substantially prevent the entrance of airbornedust particles into the switch.

As shown in FIG. 5, rotary actuator 41 may be optionally provided with aseal 65 for even more positively preventing dust and lint from eneteringhousing 21. Specifically, back wall 26 of housing 21 is shown to beprovided with a circular rib 67 concentric with the axis of post 47.Actuator member 41 is shown to be provided with a groove 69 whichreceives rib 67. Further, the outer face of actuator member 41 proximateopening 45 receiving post 47 is provided with an outwardly projectingrib 71. Seal member 65 is disposed on the exterior of the actuator andit has a groove 73 which receives rib 71. Thus, the interfitting ribsand grooves form a labryinth seal arrangement which readily permitsrotory movement of actuator member 41 so as to operate the switch partswithout appreciably increasing the force required to operate the switch,and yet effectively seals out dust and lint from the interior of theswitch. Of course, snap ring 48 may be used to hold seal 65 and rotoryactuator 41 in place on post 47.

Referring now to FIG. 4, switch 1 is shown to have a modified rotaryactuator member, as generally indicated in 41'. Generally, modifiedactuator member 41' operates in the manner similar to actuator member 41heretofor described. The primed reference characters, as shown in FIG.4, indicate portions of actuator member 41' having a similarconstruction and operation to actuator member 41 heretofor described.However, one significant difference between actuator member 41' and theactuator member heretofor described is the omission of the coilcompression spring 59 for transferring force from centrifugal actuator 9to the upper flexible switch arm 37. Specifically, rotary actuatormember 41' is provided with an integral finger 75 which slidinglyengages the bottom face of switch arm 37 and which pushes the switch armupwardly as the rotary actuator member rotates from its run to itsstarting position upon axial shifting movement of the centrifugalactuator. Since rotary actuator member 41' is a rigid integral unitpivoted for rotation about the axis of post 47, finger 75 also rotatesabout post 47 and thus the point at which it engages the bottom face ofswitch arm 37 varies along the length of the switch arm as thecentrifugal actuator moves the rotary actuator member from its startingto its stop position. Still further, in switch applications in which theswitch actuator member is subject to further movement towards itsstarting position upon the engagement of movable contact 38 with itsrespective fixed contact 31, the provision of a rotary actuator member,such as rotary actuator member 41' with finger 75 thereon, functions toat least in part limit the application of force to the switch arm whichin turn aids in reducing the stress applied to the switch arm. Asheretofore noted, switch arm 37 is cantilevered from its mountingterminal T₄. As the switch arm is moved from its run to its startingposition and as its movable contact 38 engages fixed contact 31, thesupport of the switch arm changes from a cantilevered beam fixed at oneend and freely supported at the other end to a beam which is fixed atone end and simply supported at the other end. As the centifugalactuator continues to move toward its off position after movable contacthas engaged its fixed contact 31, additional deflection of the switcharm will be effected as is generally indicated at D in FIG. 4. It willbe appreciated that the deflection D is related to the additionalmovement of the rotary actuator member 41' as the centrifugal actuatormoves into its start position. In certain instances, when thecentrifugal actuator engages the cam follower member 53' of rotaryactuator member 41' immediately upon its beginning to move from its runposition, it will be appreciated that a considerable amount ofadditional movement of the rotary actuator member may be effected afterthe switch contacts have been moved from their run to their startpositions. It is especially true that an appreciable degree of thedeflection of the switch arm 37 may be present if a centrifugal actuatornot having clyindrical holding surface 20 is used. In accordance withthis invention, as rotary actuator member 41 continues to rotate on post47, the point of contact along the length of switch arm 37 varies fromthe position L₁ shown in FIG. 4 when movable contact 38 first engagesits fixed contact 31 to a point L₂ when the centrifugal actuator isfinally in its start position. The change in length (Δ L) of the pointof contact on the switch arm serves to decrease the bending stresses towhich the switch arm is subjected even though the amount of deflection Dremains essentially the same. Because of the change of length, it ispossible, in many instances, to avoid permanent deformation of switcharm 37 so that the switch arm will readily return to its desiredcondition upon start of the motor and the switch arm will retainsufficient spring action to make good electrical contact between movablecontact 38 and fixed contact 33 when the switch is in its run position.

It will be appreciated that in regard to rotary actuator member 41illustrated in FIG. 3, the purpose of compression coil spring 59interposed between lever 55 and the bottom face of switch arm 37 is tolimit the loads of forces interposed on the switch arm by the actuatormember so as to prevent overstressing and permanent deformation of theswitch arm. It will be further appreciated that upon the free end ofswitch arm 37 engaging fixed contact 31, the compression coil spring 59(FIGS. 1-3) will compress upon further clockwise rotation of actuatormember 41 (as viewed in FIG. 3) thereby limiting the amount ofdeflection impose on switch arm 37 and thus limiting in effect theamount of bending stresses applied to the switch arm.

Referring now to FIG. 7, still another embodiment of the starting switchof the present invention is shown, this other embodiment being indicatedin its entirety at 1'. As shown, switch 1' comprises a mounting frame101 on which a switch actuator arm 103 is pivotally mounted. Thus,mounting frame 101 is generally analogous to housing 3 and actuator arm103 is generally analogous to rotary actuator member 41 heretoforedescribed. Frame 101 is shown to have a pair of movable switch arms 105and 107 cantilever-mounted thereon for opening and closing a pair ofswitches S3 and S4. it will be appreciated that switch arms 105 and 107are generally similar to switch arms 37 and 39 and that switches S3 andS4 correspond to switches S1 and S2 heretofore discusssed. Switch arm103 is pivotally mounted on frame 101 on a post 109 and, as shown inFIG. 7, it is offset mounted with respect to shaft 7 such that its camfollower end 111 moves generally radially relative to the centerline ofshaft 7. Further, arm 103 includes a pair of fingers 113 and 115engageable with respective switch arms 105 and 107 for moving or flexingthe switch arms to make or break switches S3 and S4 upon switch 101being actuated between its start and run positions by movement ofactuator member 13 as it moves between its start and run positions.

Further, switch 101 may be provided with an optional cover 117 whichsnaps in place on frame 103 to enclose and protect switches S3 and S4and their respective switch contacts from contamination by dirt, dust,or other airborne particles. The front of the cover overlying theswitches has been omitted for purposes of illustration. A spring 119 maybe included in switch 101 to resiliently bias the actuator lever 103toward switch arms 105 and 107.

As heretofore described in regard to switch 1, cover 117 fits closelyaround the hub of actuator arm 103 with a tight gap therebetween so asto inhibit the introduction of airborne dust into the interior of theswitch during operation thereof. In this manner it will be seen thatframe 101 and cover 117 cooperate with the mounting hub of the actuatorarm in a manner similar to bottom wall 25 of housing 21.

In view of the above, it will be seen that the several objects of thisinvention are achieved and other advantageous results obtained.

As various changes could be made in the above construction withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description and shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

What is claimed is:
 1. In a dynamoelectric machine, such as an electricmotor, comprising a stator, a rotor and a shaft journalled with respectto the stator and supporting the rotor, said shaft having a longitudinalaxis, said motor further including an auxiliary winding and a startingswitch operable to de-energize said auxiliary winding upon the motorobtaining a predetermined speed during start up, said motor furtherincluding a centrifugal actuator mounted on said shaft and operativelyconnected to said starting switch for actuation of the latter inresponse to said rotor obtaining said predetermined speed, saidcentrifugal actuator having a portion thereof shiftable axially uponsaid shaft between a start position and a run position upon start up ofthe motor and upon said rotor obtaining said predetermined speed andbeing shiftable in reverse direction from its run to its start positionupon slowing or stopping of the rotor thereby to reset said startingswitch, the latter having a housing adapted to be secured in fixedposition relative to said centrifugal actuator and having at least oneswitch contact therewithin movable in response to movement saidcentrifugal actuator between a start position in which said auxiliarywinding is energized and a run position in which said auxiliary windingis de-energized, said housing having a wall, wherein the improvementcomprises: an opening in said housing wall, said opening being offset toone side of said longitudinal axis of said shaft, a post secured to saidhousing and located within said opening, said post extending generallyparallel to the longitudinal axis of said shaft, an actuator memberjournalled on said post, said actuator member having a cam followerextending from said post in generally transverse direction with respectto said longitudinal axis of said shaft and being cammingly engageablewith said centrifugal actuator portion on the other side of saidlongitudinal axis from said post as said centrifugal actuator portionshifts axially between its run and start positions, said actuator memberfurther having a movable contact lever disposed within said housing andcooperable with said movable switch contact, said actuator member beingrotatable on said post in a generally radial direction with respect tosaid centrifugal actuator portion as the latter shifts axially betweenits start and run positions thereby to effect operation of said movableswitch contact between its start and run positions.
 2. In adynamoelectric machine as set forth in claim 1 wherein said actuatormember has a hub, the latter having a hub aperture therein, said hubaperture receiving said post thereby to rotatably mount said actuatormember on said post, said hub having a relatively close fit with saidhousing wall adjacent said opening whereby the movement of said hubrelative to said housing wall and the close fit between housing wall andsaid hub inhibits the introduction of particulate contaminants into saidhousing via said opening.
 3. In a dynamoelectric machine as set forth inclaim 1 wherein said centrifugal actuator portion is movable through anaxial distance relative to said shaft greater than the movement of saidcentrifugal actuator portion required to actuate said movable switch viasaid actuator member, wherein said movable switch contact includes acentilevered switch arm, and wherein said actuator member includes aspring interposed between said movable contact lever and said movableswitch contact for limiting the force applied to said movable contactarm.
 4. In a dynamoelectric machine as set forth in claim 1 wherein saidcentrifugal actuator portion is movable through an axial distancerelative to said shaft greater than the movement of said centrifugalactuator portion required to actuate said movable switch via saidactuator member, wherein said movable switch contact includes acantilevered switch arm, and wherein said actuator member includes afinger movable with said movable contact lever slidably engageable withsaid cantilever switch arm and varying the point of contact therealongas said centrifugal actuator moves through its full distance thereby todecrease stresses on said cantilever switch arm.